The invention relative to a valve drive of an internal combustion engine with the following characteristics:
a) the valve drive includes of a hydraulic support element, a finger lever and a cam of a camshaft or a plurality of these structural parts;
b) the support element is installed with its housing into a cam-side bore of a cylinder head, whereby a pressure piston that is axially movable relative to the housing and located in a bore of the housing projects with its head beyond the cylinder head in the direction of the cam, whereby between a bore-side bottom of the housing and a bore-side web of the pressure piston, a high pressure chamber for a hydraulic medium is located, which high-pressure chamber can be closed by a closing body of a check valve attached to the web in the direction toward a supply chamber or a supply line enclosed by the pressure piston;
c) the finger lever is constructed like a beam and has lateral surfaces near the cam and away from the cam, whereby it acts via a first end of the lateral surface away from the cam on at least one gas exchange valve in the direction of the stroke and is supported via a second end of the lateral surface away from the cam on the head of the pressure piston so that it can move by pivoting;
d) the cam acts on a contact section that lies between the ends of the cam-side lateral surface of the finger lever.
A valve drive of this type is known from the prior art from the document "Hydraulic Valve Lash Adjustment" (page 9) from August 1996, published by the applicant. It is disadvantageous in this that eccentricity of the cam base circle, transverse oscillations of the camshaft, brought on for example by auxiliary cams for injection pumps, or camshaft bearing play in the base circle can cause the high pressure chamber of the hydraulic support element to become hardened and the gas exchange valve opens in a most unfavorable way. Even in so-called transient operation of the engine, in particular during extremely cold environmental temperatures, the fall rate of the hydraulic support element is not sufficient to compensate for the positive dilatations on the gas exchange valve involved, preferably the outlet valve. In addition, in hydraulic support elements that have been constructed until now, a closing structure of its check valve must be opened with motor oil pressure. Thus, a certain time delay until the completion of the play compensation must be taken into account. This delay is a function of the instantaneous differential pressure incident on the check valve.
The object of the invention is thus to create a valve drive of the above-mentioned type, in which the cited disadvantages are eliminated.